Transmit beamforming is a signal processing technique that uses two or more antennas at a transmitter to increase the signal to interference plus noise ratio (SINR) at a receiver and, thereby, the rate at which data can be communicated from the transmitter to the receiver. The basic operation of transmit beamforming is to send the same signal to the receiver from each of the two or more antennas. However, a different beam weight (or set of beam weights) is applied to the signal sent from each antenna.
In order to improve the SINR at the receiver, the values of the different beam weights (or sets of beam weights) are not arbitrarily chosen. Rather, they are determined based on knowledge of the wireless channel used to convey the signal between the transmitter and the receiver. Once determined, the different beam weights (or sets of beam weights) can be normalized to ensure a fixed overall transmit power from the transmitter. However, normalization can be performed in several different ways (based on different power constraints) and, depending on the method of normalization used, the bit error rate (BER) or block error rate (BLER) of the data sent to and decoded at the receiver can vary.
Therefore, what is needed is a method and apparatus for selecting the normalization technique used to normalize the different beam weights (or sets of beam weights) in order to improve the BER or BLER of the data decoded at the receiver.
The present invention will be described with reference to the accompanying drawings. The drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number.